Energy absorbing structures are commonly incorporated into vehicles and other structures to protect personnel, structure, and/or property against impulsive loads associated with a dynamic event, such as an impact, blast, or a crash. As illustrated in FIG. 1, an energy absorbing structure 10 is designed to absorb the energy associated with an impacting object or pressure wave 11 by locally and/or globally buckling and thereby protecting the personnel, structure, and/or property within the vehicle or other structure 12 incorporating the energy absorbing structure 10. For instance, energy absorbing structures are commonly used as fail-safe mechanisms in vehicles to prevent damage to critical components of the vehicle and mitigate the harm to passengers in the event of a mechanical failure or crash.
As illustrated in FIGS. 2A and 2B, related energy absorbing structures 10 are cylindrical tubes having a facesheet 13 and either a honeycomb core or a corrugated core 14 bonded to the facesheet 13. Related energy absorbing structures 10 are generally limited to cylindrical tubes because honeycomb and corrugated cores 14 cannot be formed into complex curvatures or shapes having small radius of curvature bends. However, cylindrical energy absorbing structures may not be the most efficient shape, depending upon the application of the energy absorbing structure. Additionally, related energy absorbing structures are not configured to perform additional functions, such as functioning as conduits for electrical wiring or fluid flow, because honeycomb cores have fully closed cells and corrugated cores have only unidirectionally open cells (i.e., the architecture of the related core materials is not well-suited for non-structural functions).
Related energy absorbing structures also have uniform stiffness and strength throughout the structure. The uniform stiffness and strength of related energy absorbing structures, however, do not allow for control over the buckling load, mode shape, and progression of the structure during a dynamic event, such as an impact, blast, or crash. Accordingly, related energy absorbing structures commonly incorporate one or more buckling initiation features to control the buckling load, mode shape, and progression of the structure. However, such buckling initiation features reduce the overall strength and stiffness of the structure and add to the complexity of the manufacturing process.